added changelog file

Author: jricher

CHANGELOG.md

@@ -0,0 +1,20 @@
+Unreleased:
+	- Added changelog
+
+*1.3.1*:
+	- Added End Session endpoint
+	- Fixed discovery endpoint
+	- Downgrade MySQL connector dependency version from developer preview to GA release
+
+*1.3.0*:
+	- Added device flow support
+	- Added PKCE support
+	- Modularized UI to allow better overlay and extensions
+	- Modularized data import/export API
+	- Added software statements to dynamic client registration
+	- Added assertion processing framework
+	- Removed ID tokens from storage
+	- Removed structured scopes
+
+*1.2.6*: 
+	- Added string HEART compliance mode